Vacuum switch



J. E. JENNINGS VACUUM SWITCH Filed May 13, 1955 April 29, 1958 VENTO/Q JO EMMETT L/E/V/V//VGS ,l gill',

/7/5 ATTR/VEY United States Patent Of VACUUM SWITCH Jo Emmett Jennings, San Jose, Calif., assignor to Jennings Radio Manufacturing Corporation, San Jose, Calif., a corporation of California Application May 13, 1955, Serial No. 508,099

6 Claims. (Cl. 200-144) My invention relates to electrical switches enclosed within a vacuumized envelope.

The principal object of my invention is to provide a switch in which the moving contact does not bounce from the fixed contact when the circuit through the switch is closed.

Another object of my invention is the provision of a switch which remains closed when surge currents occur in the circuit.

Another object is the provision of a switch capable of carrying high voltages and currents; and in which engagement of the Contact parts is first completed with negligible physical resistance which then rapidly increases to bring the moving contact parts to a full stop with no tendency whatever to bounce.

Another object of the invention is the provision of contact points which supply in their resilience the total energy, or nearly the total energy, needed to overcome by pressure applied in a direction transverse to their line of movement, their closing pressure and momentum.

The invention possesses other objects, which with the foregoing will be brought out in the following description of the invention. I do not limit myself to the show- `-ing made by the description and drawing, since I may adopt variant forms of the invention within the scope tof the appended claims.

Referring to the drawings:

Fig. l is a vertical half sectional view of my switch.

Fig. 2 is a fragmentary view in elevation taken in the direction indicated by the arrow 2in Fig. 1, and showing the contact structure of my switch.

Fig. 3 is a sectional View taken in the plane 3-3 of Fig. 2, and showing the position of the parts when the contacts are closed.

Fig. 4 is a fragmentary view in section similar to Fig. l, but showing the contacts when the switch is open.

In a switch having aligned contact rods in which one of the contacts is moved to engage the other to`close the circuit, the problem presented by the tendency of the moving contact to bounce after first engagement has been a troublesome one. In one of my-switches using tungsten contact rods, I have observed as many as five different bounces or successive contacts before the final closing@ The greater' the travel of the moving contact rod, and the greater force applied, the more bounce. I have found that with a moving contact rod of small mass and short travel, a much better electrical contact resulted with very little bouncing, but this works only on low power, and is not satisfactory for high voltage or current where complete absence of any tendency to bounce seems the only answer.

My present invention deals with a structure in which the switch contacts close without bouncing; and I accomplish this by providing a plurality of fixed and stifiiy resilient spaced contact rods aligned with and engageable with a movable wedge-end contact rod, and all so proportioned and arranged that when the movable contact moves into engagement with thefixed contactr assembly Patented Apr. 29, I1958 2 to close the circuit through the switch, there is first a complete closing engagement between two sets of contact surfaces, followed almost instantly by the homing or final seating of the wedge-end contact in the fixed contact assembly.

At the very first engagement of the contact surfaces, the advancing thrust of the wedge-end contact is resisted by the fixed assembly, the transverse component of the actuating force plus the momentum of the moving wedgeend contact being absorbed in the stiffly resistant fixed contact assembly, with the result that the moving contact is literally braked to a full stop with the contacts in continuous engagement from the initial touching, and consequently, with no bouncing.

With the opening of the switch, the engagement between the contact surfaces is fully maintained during vthe initial opening movement, and then instantly broken as the wedge-end contact leaves the fixed contact assembly;

My switch is enclosed in the glass vacuumized envelope 2 closed at one end by the copper or other rigid metallic terminal cap 3 in whichthe copper end plug 4 is brazed. This plug provides the mounting for the fixed tungsten Contact rods of which there are two sets 6 and 7. As shown, I employ two sets of these rods, opposed in pairs, each set having four rods, and all arranged in parallelism.

By properly heating the tungsten rods before assembly, l can modify the molecular structure of the metal so that the rods remain resilient even through the high temperature to which they may be subjected during evacuation of the envelope or later during use of the switch. This retention of resilience in the contact rods is of very great importance in the proper functioning of my switch; and makes unnecessary any other spring for that purpose.

The two sets of Contact rods which conveniently are cylindrical are brazed into the mounting plug to lie in parallelism; and the free ends 8 and 9 are beveled on the inside as shown, so that when seated on the wedgeend contact 12, the wedge portion 13 spreads the two sets of stifiiy resilient rods apart.

Fig. 4 shows the wedge-end contact spaced from the beveled ends of the fixed contact rods in the open position of the switch; and the proportions and arrangements of the parts are such that as the wedge-end contact is moved toward the fixed contact rods by atmospheric pressure, the small edge of the wedge engages firmly between the beveled ends of the stiff rods, and from the rst touching forms a full physical engagement for the conduction of the current. The further engaging movement of the wedge-end contact seats the wedge within the fixed contact rods and the shoulders 14 against the points of the rods as shown in Fig. 1, at which time the fixed rods which have been forced apart and out of parallelism, bear firmly and resiliently against the wedge 13, so that the contacts remain fully engaged without bouncing. The pressure of the fixed contact rods upon the wedge-end contact due to their resilience under dis-v placement, is increased by their inductance due to the passage of high currents through them, and this too tends to suppress the effects of surge currents.

Since the contact points are brought together and separated in a high vacuum, the contact surfaces remain un contaminated, and contact resistance remains a very low` value.

The wedge-end contact 12 which moves toward and away from the fixed contact rods to make or break the circuit through the switch, is a generally rectangular tungsten block brazed into a coppercup 16, essentially mounted on the inner end 17 of the copper bellows 18V which with the rigid metallic end cap 19 closes the end ofthe glass envelope. Between the cup and the bellows, a'

shield 20 is disposed, offset central portions as shown, being provided on shield and bellows ,end to facilitate aligned assembly and brazing of the parts.

The outer end of the bellows, formed as a sleeve 21, is brazed within the cylindrical head of the end cap 19; and within the sleeve is brazed the bearing tube 22 in which the actuating stem 23 for the wedge-end or-movable contact 12 has its slide bearing. The inner end of the stern is brazed into the central depression in the bellows end, and the outer end is threaded for connection with an operating means such as a solenoid by which the movable contact can be pulled out of engagement with the fixed Icontact rods.

From the above it will be clear that when tl e switch is closed, the complementary contact surfaces of the rods and the wedge are in full engagement over a broad area as shown in Fig. l. At this time each of the pairs of rods are spread apart a small amount at their free ends, the amount of deflection and the resilience of the rods being such as to maintain a firm pressure betwccn the complementary contact faces past which a heavy current may be flowing.

When the switch is actuated to open the circuit, the wedge contact is withdrawn, the resilient rods maintainingirm engagement with the wedge up to the moment when the actual break occurs between them. At this point the rods regain their parallelism and the wedge stops when the required separation is reached. The parts are then as illustrated in Fig. 4. The plurality of rods insures an ample conductive path with sufficient contact area while preserving the desired resilient contact pressure throughout the opening or closing operation.

Although my switch has a wide application, for general use, its special qualities particularly fit it for use where extremely high starting currents are required, such for example as in capacitor switching, motor starters, transformers, spot Welders and many others. k In constructing my switch, the fixed rod assembly is disposed in one half of the envelope; and the movable wedge-end assembly disposed in the other half. halves are then brought together and joined at the bead 26, the contacts being engaged as in Fig. l to insure alignment. The envelope is then exhausted and the tubulation sealed off.

I claim:

l. A Vacuum switch comprising a vacuumized glass envelope, a rigid metallic end cap constituting a terminal closing one end of the envelope, laterally resilient Contact rods fixed in the end cap, a second rigid metallic end cap constituting a terminal arranged on the other end of said envelope, a bellows open on the inside thereof tolatmosp'heric pressure and integrally united with the second end cap and extending into the envelope and with said second end cap closing said other end of said envelope, a wedge-end contact tixed on the inner end of the bellows in alignment with the iixed laterally resilient contact rods to wedge them apart when moved by the expanding bellows into engagement therewith, and means within the bellows and extending out of the envelope for operatively controlling the movements of the bellows.

2. A vacuum switch comprising a vacuumized glass envelope, a copper end cap constituting a terminal hermetically united to and closing one end of the envelope, a plurality of pairs of `Contact rods ti ed in the end cap with corresponding rods ofeach pair in parallelism, a second metallic endvcap constituting a terminal directly and rigidly ixed hermetically on the other end of said envelope, a bellows integrally united with the second end cap and extending into the envelope and with said second end cap closing said other end of the envelope, a wedge-end contact fixed on the inner end of the bellows in alignment with the iixed contact rods to wedge the rods of each pair apart when moved by the bellows into engagement therewith, and means within the bellows and extend` ing out of the envelope for operatively controlling the movements of the bellows.

The

3. A vacuum switch comprising a vacuumized glass envelope, a rigid metallic end cap constituting a terminal closing one end of the envelope, a pair of opposed laterally resilient contact rods fixed in the end cap, a second rigid metallic end cap constituting a terminal arranged on the other end of the envelope, a bellows integrally united with the second end cap and extending into the envelope and with said second end cap closing said other end of the envelope, a shield plate on the inner end of the bellows, a mounting means on the shield plate, a wedge-end contact on the mounting means, said bellows and shield plate and mounting means and contact having interengaging portions and being brazed together in an integral unit in operative alignment with the fixed Contact rods, and means Within the bellows and extending out of the envelope for operatively controlling the movements of the bellows.

4. In a vacuum electrical switch including a vacuumized envelope, a metal mounting block lconstituting a terminal, a plurality of pairs of opposed Contact rods integrally fixed in the block, each rod being stitliy resilient and integrally united with the block, a wedge-end contact in axial alignment with the contact rods, said rods and wedge-end contact having complementary engaging surfaces proportioned to progressively laterally displace and resiliently stress opposed rods of each pair from a minimum at rst contact to a maximum at full engagement of the complementary engaging surfaces, a second terminal, and means integral with the second terminal and the wedge-end contact for movino the wedge-end contact axially toward or away from the contact rods.

5. A vacuum switch comprising a vacuumized envelope, an end cap constituting a terminal closing one end of the envelope, a second end cap constituting a terminal arranged on the other end of the envelope, a plurality of pairs of resiliently flexible rods lixed at one end in the first said end cap and at their free ends con stituting a plurality of pairs of opposed contacts, each pair of opposed contacts having a wedge-shaped gap therebetween, a bellows within the envelope and integrally united with the second end cap to close the other end of said envelope, a wedge-shaped contact fixed on the bellows within the envelope in operative alignment with the plurality of gaps between opposed pairs of contacts, and

(iii

means within the bellows and outside the envelope for operatively controlling the engagement and disengagement of the Wedge-shaped contact with the plurality of` pairs of opposed contacts.

6. In an electrical switch, the combination comprising a metal mounting block constituting a terminal, a plurality of pairs of opposed contact rods integrally lixed in the block, the rods of each pair being stili'ly resilient and extending into the envelope to provide free end portions having divergent contact surfaces, a wedge-end contact in alignment with the contact rods and having engaging surfaces sloped to complement said divergent contact surfaces on full engagement thereof, and stop means on said wedge-end contact adapted to abut the free ends of said rods to limit inward movement of the wedge-end Contact.

' References Cited in the tile of this patent UNITED STATES PATENTS 1,891,736 Greenwood Apr. 2l, 1931 1,814,851 Prince Iuly14, 1931 1,978,246 Bauerschmidt Get. 23, 1934 1,988,687 Jackson Jan. 22, 1935 1,996,304 Millikan et al. Apr. 2, 1935 2,121,180 Vatter June 2l, 1938 2,155,974 Doau May 2, 1939 2,306,117 Dunlap Dec. 22, 1942 2,740,869 Jennings Apr. 3, 1956 FOREIGN PATENTS Y 703,177 Germanyy Mar. 3, 1941 

